Abstract Maternal depression is a serious disorder that not only negatively impacts the depressed woman but also has long-lasting negative consequences on her child. Specifically, the increased risk of mental health problems in the child persists over the lifecourse and is again transmitted to the next generation. Although maternal depression treatments are available, the degree to which they causally shift the child's socio-emotional, cognitive, and physical development trajectory is less well understood. Importantly, randomized controlled trials comparing multiple depression interventions have not been well equipped to answer this important question due to insufficient follow-up periods; the interventions beginning after the most sensitive developmental periods; or lack of appropriate comparison groups. The success of a given intervention depends on multiple factors, with a key modifiable factor being the extent to which an intervention can alter the parenting behaviors of the depressed woman. Our long term objective is to identify key modifiable factors in the intergenerational transmission of risk from a depressed mother to her child. The goal of this study is to rigorously evaluate the impact of a perinatal depression intervention that starts prenatally and continues through 6 months post-partum, on child development. We will achieve this by combining, and fully integrating, with a funded perinatal depression intervention clustered RCT (SHARE: U19MH095687). In addition to enrolling the depressed women who will participate in the SHARE trial, we will also enroll a subset of non- depressed women, and follow-up the mother-child dyads for at least 36 months post-partum. Enrolling the not depressed mothers enables us to determine the extent to which the intervention can lead to equivalence between the treated depressed and non-depressed groups as well as to identify potential positive externalities to non-depressed women in the intervention arm. Together, these approaches will yield decisive evidence of the causal impact of a perinatal depression intervention on child developmental outcomes. We hypothesize that depression intervention will improve child outcomes relative to the control group, and we will examine whether it will also result in the convergence of outcomes to those children whose mothers were not depressed prenatally. We will also analyze potential mediators focusing on whether improved parenting quality is an important mechanism linking the depression intervention and child outcomes. Finally, we will determine how the relationship between participating in the intervention and child outcomes varies by factors such as family composition, socioeconomic status, and exposure to interpersonal violence. We expect the results of this research to inform the design of future perinatal depression interventions that will have the greatest protective impact on future generations.